Hammer with a ram control device

ABSTRACT

The invention relates to a hammer comprising a hydraulically operated ram and a control device for stopping the ram, comprising a piston and cylinder combination, one end of which is permanently in communication with a hydraulic fluid cavity, and the other end being in communication with said cavity through a main switching device, a pump draws liquid from a reservoir and pressurizes the cavity, as well as supplying fluid to the upper end of the cylinder through a non-return valve from the cavity, the main switching device communicating with the reservoir through a passage in which is provided an escape valve and a throttle in said passage, and a further throttle in a branch passage communicating with said first mentioned passage in front of the throttle, a switch piston occupying a cylinder behind the further throttle to control the escape valve through an actuator operated by the switch piston.

United States Patent 91 Hassel Apr. 17, 1973 [75] Inventor: Harald Hassel, Coburg, Germany [73] Assignee: Langenstein & Schemann Aktiengesellschaft, Coburg, Bavaria, Germany 22 Filed: Sept. 17, 1970 21 Appl.No.: 73,064

UNITED STATES PATENTS Kay Cordes et a1. ..9 H321 FOREIGN PATENTS OR APPLICATIONS 1,243,949 7/1967 Germany ..9 H321 Primary Examiner Paul E. Maslousky AttorneyHolman and Stem 5 7 ABSTRACT The invention relates to a hammer comprising a hydraulically operated ram and a control device for stopping the ram, comprising a piston and cylinder combination, one end of which is permanently in communication with a hydraulic fluid cavity, and the other end being in communication with said cavity through a main switching device, a pump draws liquid from a reservoir and pressurizes the cavity, as well as supplying fluid to the upper end of the cylinder through a non-return valve from the cavity, the main switching device communicating with the reservoir through a passage in which is provided an escape valve and a throttle in said passage, and a further throttle in a branch passage communicating with said first mentioned passage in front of the throttle, a switch piston occupying a cylinder behind the further throttle to control the escape valve through an actuator operated by the switch piston.

6 Claims, 3 Drawing Figures PATENTEDAFR 1 71975 sum 1 HF INVENTOR fir n ers PATENTEU 3.727. 519

sum 3 0K3 FIG. 3

HAMMER WITH A RAM CONTROL DEVICE The invention concerns a hammer of the kind having a hydraulically operated ram and a fluid pressure actuated control device for stopping the ram, the control device comprising a piston, slidably mounted in a cylinder, to which fluid under pressure can be admitted, a lower end of the cylinder being permanently in communication with a hydraulic fluid cavity and fluid entry to the upper end of the cylinder being controlled by a main switching device, a pump arranged for drawing fluid from a reservoir and for pressurizing the cavity and also to supply fluid to the upper end of the cylinder through a passage which provides communication from the upper end of the cylinder through nonreturn valve to the hydraulic fluid cavity and a passage which is provided with a shut-off valve, from the main switching device to the reservoir.

It is well known that, as a result of the extreme differences of the re-coiling speeds, it is difficult to stop the re-coiling ram at the same position on each stroke. As a solution for this problem it has been proposed to provide a second piston-cylinder-unit which is actuated after control of pressure in the upper end of the cylinder and the length of the stroke stays the same, independent of the height of the die. This solution, however, has the disadvantage, that the piston-cylinder-unit is very big and that its size varies in dependance upon the size of the hammer. In addition installation is only possible at great expense.

It is the object of this invention to create a less expensive arrangement, which furthermore, is independent of the size of the hammer and can also easily be fitted in later, by retaining the advantage that the length of stroke is independent of the height of the die.

The invention provides a hammer comprising a hydraulically operated ram and a control device for stopping the ram during its return stroke comprising a hydraulically operated piston slidably mounted in a cylinder, a lower end of the cylinder being in communication with a hydraulic fluid cavity, fluid pressure entry to an upper end of the cylinder being controlled by a main switching device,a pump for drawing fluid from a reservoir and for pressurizing the cavity and also to supply fluid to the upper end of the cylinder through a passage which provides communication means from the upper end of the cylinder through a non-return valve to the hydraulic fluid cavity, a passage which is provided with a shut-off valve, from the main switching device to the reservoir, a throttle situated in said passage which leads from the main switching device to the reservoir a further throttle in a branch passage communicating with said passage upstream of said throttle, a switch piston occupying a cylindrical cavity behind the further throttle and the shut-off valve being actuated by an actuator which is operated by the switch piston.

The control device, according to the invention, can either be fitted into a normal top-pressure hammer or into a counter blow hammer for its upper ram, whereby the hammer can operate vertically or horizontally. The lower end of the cylinder remaining for instance either in communication with the hydraulic fluid cavity of an accumulator, or with a fluid amplifier. The pump according to the invention, is provided in theusual way with a pressurizing valve and a pressure relief valve.

The switch piston is pushed into the cavity in which it projects, by means of pressure or elasticity.

The invention will now be described by way of example with reference to the accompanying drawings in which,

FIG. 1 is a'view of a hydraulically operated hammer with control device constructed in accordance with the invention and FIG. 2 is a cross-section of the control device shown in FIG. 1, and on a larger scale.

FIG. 3 is an enlarged cross-sectional view of part of FIG. 1.

Arranged in a hammer-frame 1 is a ram 2 mounted for up and down motion. Arranged below the ram 2 is an anvil 1b which is fixed into the hammer-frame l. The ram is connected to a ram piston 4 by means of a ram piston rod 3, the piston is acted upon by hydraulic fluid entering the upper end 5 of a cylinder 6a or the lower end 6 of the cylinder. Provision is made for the upper end 5 of the cylinder 6a and the lower end of6 of the cylinder within the hammer-frame 1, above the ram 2. A passage 9 leads from a pump 7, which is provided with a pressure relief valve 16, and a pressurizing valve 8 to a gate valve 10 and also to the lower end 6 of the cylinder 6a.

The gate valve 10, as seen in FIG. 3, has a body 50 in which there are three axially spaced chambers 51, 52 and 53 respectively. These chambers communicate with an axial bore 54. A spool 55 which is slidably mounted within the bore 54 has respective pistons 56 and 57 which are interconnected by a rod 58. The pistons 56 and 57 are a sliding fit in the bore 54.

Passages 18 and 9 communicate with the chambers 52 and 53 respectively. The position of the spool is controlled by control means 67 and 68 connected to respective pipes 69 and 70 which communicate with respective ends of the bore 54. The control means 67 and 68 control flow of hydraulic fluid through the pipes 69 and 70 respectively. The chamber 51 communicates through a pipe 59 with a chamber 60 ofa shut-off valve 19 which together with a valve 19a forms valve means for shutting-off flow from the chamber 5 to the reservoir.

This shut-off valve 19 has a further chamber 61 which is axially aligned with and spaced from the chamber 60. These chambers 60 and 61 communicate with an axial bore 62. A spool 63, which is slidably mounted within the bore 62 has respective pistons 64 and 65 which are joined by a rod 66. The spool pistons 64 and 65 are a sliding fit in the bore 62.

The spool 63 is shown in its right-hand position. The chamber 61 communicates with a passageway 27 of a control device 20.

A valve 19a is operated electrically from an actuator 38 which is controlled in a manner to be described. The valve 19a allows hydraulic fluid to flow to either side of the shut-off valve so as to control the position of the spool 63. A passage 11 leads from the passage 9 to a hydraulic fluid cavity 12 of an accummulator 13. The pressure relief valve 16 is arranged in a passage 16a which leads into a reservoir 22. The hydraulic fluid, which is in the hydraulic fluid cavity 12 remains under high pressure, which is created by a gas in a closed cavity l4 acting on a piston 15 which in turn acts on the hydraulic fluid in the hydraulic fluid cavity 12. The accummulator 13 can be replaced by a fluid amplifier.

The lower end 6 of the cylinder 6a remains in open contacts with the hydraulic fluid cavity 12 through the passage 1 1. The upper end of the cylinder can be connected to the hydraulic fluid cavity 12 and to the lower end 6 of the cylinder through the passages 17 and 18 the gate valve and the passages 9 and 11. Further, a connection to the reservoir 22 can be made through the passages 17 and 18, the gate valve 10, the shut-off valve 19, the control device 20, and through a passage 21. A further connection to the upper end 5 of the cylinder 6a to the hydraulic fluid cavity 12 can be made through the passage 17 and a further passage 23 and a nonreturn valve 24. A further connection between the reservoir 22 and the upper end 5 of the cylinder can be made through the passages 21, 25, 18 and 17. The passage 25 contains a non-return valve 26 allowing flow from 21 to 18 only.

As shown in FIG. 2 situated in the control device is the first passageway 27 having a throttle 28, which connects the shut-off valve 19 to the passage 21. The passageway 27 is connected to a cavity 30 through a branch passage 27a and through a further throttle 29,

which can be adjusted by means of a small piston 39.

The further throttle 29 is an opening in a tube 39a which extends through the cavity 30, and in which the small piston 39 can be moved. The cavity 30 is in communication with the reservoir 22 through a passage 33 and past a third throttle 32, which can be adjusted by means of a small piston 31. The third throttle 32 is an opening in a tube 310, in which the small piston 31 can be moved. The adjustment of the small pistons 31 and 39 can be accomplished by means of nut and bolt devices 32a and 29a.

A movable switch piston 34, which is situated in a cylindrical cavity 36, extends into the cavity 30. The piston 34 is pushed into the cavity by pneumatic pressure in a cavity 35. In an alternative construction it is pushed into the cavity 30 by means of a spring. The switch 34 has an extension 34a which enters the cavity 35. A further piston 40, carrying a switching disc 44, occupies a cylinder 43 which is in communication with the passageway 27 through a passage 41. The further piston 40 has an extension 40a occupying a cavity 42 and is moved downwards by means of a spring. The cylindrical cavity 36 and the cylinder 43 have communication with the upper end 5 of the cylinder through apassage 37. Further, the actuator 38, which can be switched by the piston 34 and the further piston40, is provided, which may for example be a de-energizing switch which alters the setting of the valve 19a which moves the spool 63 to the left by hydraulic pressure. The cavity is supplied with compressed air through a passage 35a from whence it can reach cavity 42 through a passage 42b. I

The action of the control device, shown in the drawings, is as follows:

The downstroke of the ram is caused by hydraulic fluid being pumped into the chamber 5. Firstly the control means 67 is operated to move the spool 58 to the right. The pressurized fluid flowing through the passage 9, then flows through the bore 54 and out through the passage 18, through the passage 17 and into the chamber 5. This pressure is also applied to the ram piston 4 in the cylinder 6a by pressurized fluid from the passage 9.

The control device has the exclusive aim of controlling the return throw of the ram 2. Therefore only the upwards motion of the ram is of interest. its speed depends on the force with which the ram re-coils from the anvil 1b. During the upwards motion of the ram 2, the liquid from the upper end 5 of the cylinder 6a flows through a bore 5a, the passages 17 and 18, a flow path 10a in the bore 54, the gate valve 10, the connection 59, a flow path 190 in the bore 62 and'the shut-off valve 19 which is now in its final position on the left, through the control device 20 and the passage 21, into the reservoir 22. The stream of fluid passes through the passageway 27 during this process. A restriction is produced by the first throttle which causes a pressure drop from the passageway 27 to the cavity 30. The. i

switch piston 34, which is pushed down with relatively small force by the compressed air in the cavity 35, starts to rise. As soon as the switch piston 34 engages the actuator 38, it switches the shut-off valve 19, electro pneumatically or electro hydraulically, back into the illustrated starting position on the right and stops the flow of fluid from the upper end 5 of the cylinder into the reservoir 22. The controlling of the shut-off valve 19 takes place in such a way that the actuator 38 opens the control valve 19a by means of an electric circuit 38a, the control valve is disposed in a control circuit 19b, through which control fluid is fed for moving the shut-off valve 19. The hydraulic fluid from the upper end 5 of the cylinder 6a is now forced into the hydraulic fluid cavity 12 through the bore 5a and the passages 17 and 23 and the non return valve 24 and a bore 12a and the ram 2 is brought to a stand-still by the back-pressure in the hydraulic fluid cavity 12 and by its own weight. The .re-coiling ram travels a certain distance, in different periods of time which decrease as the upwards speeds of the ram increase. The higher the recoil of the ram is at the blow, the earlier the shut-off valve 19, must be switched off, so that the greater travel does not affect the total stroke. 'The control device 20 fulfills this condition, because the higher the re-coiling speed of the ram 2, the higher the speed of the flow through the first throttle 28, the higher is also the static pressure in front of the first throttle 28, therefore the flow through the first throttle 29 is greater. Accordingly the switch piston 34 rises quicker and the actuator 38 switches the shut-off valve 19 over earlier.

However, sometimes the effect obtained is not sufficient. Therefore the third throttle 32 has been added, which compensates the effect of the further throttle 29 in the following way:

As soon as the switch piston 34 is lifted, a pressure is produced in cavity 30, which is determined through the compressed air or spring loading of the switch piston 34. Therefore a pressure drop exists between the cavity 30 and the passage 33, which is connected with the reservoir 22. Therefore hydraulic fluid escapes through the third throttle 32. The amount is proportional to the lifting time of the switch piston 34, that is to say, more liquid flows through the third throttle 32 if the switchpiston rises slowly, and little if it rises quickly.

A relatively accurate anticipation of the necessary switching-off time for the entire range of recoiling speeds occuring in normal drop forgings can be obtained with the throttles 29 and 32. For the impact of a ram on a smooth plate it is necessary to accept a certain overthrow, or the further piston 40 has to be utilized. Normally this piston is not put into action because it is loaded by fluid in the cavity 42. Only if an unusually high pressure is produced in the passageway 27, as a result of an extremely large re-coil, the piston can overcome the pressure in cavity 42. The switch-disc 44 of the further piston 40 will then engage the actuator 38, which causes the switching off process.

The control device operates like a hydraulic timing relay, which starts to run down with the beginning of the throw of the ram 2, the period of travel being dependent only upon the pressure in the passageway 27 and on the setting of the throttles 29 and 32, which can be accomplished through the pistons 31 and 39. The height of the stroke of the ram 2 is therefore independent of the size of the hammer. Only the first throttle 28 is modified, depending on the size of the hammer.

The cylindrical cavity 36 and the cavity 43 are permanently in communication with the upper end 5 of the cylinder through the passage 37. If the upper end 5 of the cylinder is subjected to pressure, this pressure is transmitted through the passage 37 so that the movement of the switch-piston 34 and of the further piston 40 is prevented. if the upper end 5 of the cylinder is opened by the gate valve 10, a pressure impulse is produced in the passage 21, as well as in the passageway 27. Through the passage 37 the pressure impulse is rendered inoperative for the control device 20, because pressure release occurs, proceeding from the gate valve 10 up to the upper end 5 of the cylinder and from there through passage 37 to the cylindrical cavities 36 and 43. This occurs after the pressure impulse in the passageway 27 has long been dispersed.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

l. A hammer comprising a hydraulically operated ram and a control device for controlling the return movement of the ram comprising a fluid pressure operated ram piston slidably mounted in a cylinder, a

lower end of the cylinder being in communication with a hydraulic fluid cavity, fluid pressure entry to an upper end of the cylinder being controlled by a main switching device, a pump for drawing fluid from a reservoir and for pressurizing the fluid cavity and also to supply fluid to the upper end of the cylinder, through a passage which provides communication means from the upper end of the cylinder through a non-return valve to the hydraulic fluid cavity, a passage which is provided with a shut-off valve from the main switching device to the reservoir, a first throttle situated in said passage which loads from the main switching device to the reservoir, a further throttle in a branch passage communicating with said passage upstream of said first throttle, a switch piston occupying a cylindrical cavity behind the further throttle, and the shut-off valve being actuated by an actuator which is operated by the switch piston.

2. A hammer according to claim 1 wherein a third throttle is arranged parallel to the first mentioned throttle which is in continuous communication with the cavity and, through a passage with the reservoir.

3. A hammer according to claim 2 wherein the further mentioned throttle and the third throttle an adjustable.

4. A hammer according to claim 1 wherein a further switch piston is provided, a portion of the further switch piston being in continuous communication with the passage having the first throttle, at a position before said first throttle, the actuator being actuated by the further switch piston.

5. A hammer according to claim 4, wherein the switch pistons are held by fluid pressure supplied from the upper end of the cylinder.

6. A hammer according claim 4, wherein the first switch piston and the further switch piston are actuated by means of fluid pressure which is fed through a shared line. 

1. A hammer comprising a hydraulically operated ram and a control device for controlling the return movement of the ram comprising a fluid pressure operated ram piston slidably mounted in a cylinder, a lower end of the cylinder being in communication with a hydraulic fluid cavity, fluid pressure entry to an upper end of the cylinder being controlled by a main switching device, a pump for drawing fluid from a reservoir and for pressurizing the fluid cavity and also to supply fluid to the upper end of the cylinder, through a passage which provides communication means from the upper end of the cylinder through a non-return valve to the hydraulic fluid cavity, a passage which is provided with a shut-off valve from the main switching device to the reservoir, a first throttle situated in said passage which leads from the main switching device to the reservoir, a further throttle in a branch passage communicating with said passage upstream of said first throttle, a switch piston occupying a cylindrical cavity behind the further throttle, and the shut-off valve being actuated by an actuator which is operated by the switch piston.
 2. A hammer according to claim 1 wherein a third throttle is arranged parallel to the first mentioned throttle which is in continuous communication with the cavity and, through a passage with the reservoir.
 3. A hammer according to claim 2 wherein the further mentioned throttle and the third throttle an adjustable.
 4. A hammer according to claim 1 wherein a further switch piston is provided, a portion of the further switch piston being in continuous communication with the passage having the first throttle, at a position before said first throttle, the actuator being actuated by the further switch piston.
 5. A hammer according to claim 4, wherein the switch pistons are held by fluid pressure supplied from the upper end of the cylinder.
 6. A hammer according claim 4, wherein the first switch piston and the further switch piston are actuated by means of fluid pressure which is fed through a shared line. 